The paper presents a double use of the EIS (environmental information system) network for scheduling thermal electricity generation with regard to ecological conditions (air quality in the vicinity of thermal power plants), and for control of the thermal loading of important transmission lines with regard to meteorological conditions. The Slovenian ecological monitoring system was set up fifteen years ago with the task of assuring acquisition of data about air pollution in the vicinity of thermal power plants. In the meantime it has been constantly upgraded and improved. At the end of 1994 Immission, emission and meteorological data started to be online transmitted to the National Dispatching Centre. Problems with space and restrictions encountered at the construction of new transmission lines made researchers look for solutions that would allow a greater loading of transmission lines without threatening power system reliability. A method was consequently theoretically implemented by monitoring of the thermal loading of the most important 400 kV transmission lines supported with meteorological data obtained from the EIS measuring system. Transmission of data from the EIS into the dispatching centre, supported with adequate software, will facilitate efficient control of the power system with consideration of ecological limitations (electricity production in thermal power plants) and, at the same time, allow more efficient exploitation of transmission lines in view of meteorological conditions. The main idea of this paper is the use of the same meteorological system for controlling both thermal generation and the loading of important 400 kV overhead lines.